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Bronze

RSVP , TE

Hi everybody

 

Please consider the following example:

 

R1---------R2----------R3----R4

                 |                |

                 |                |

                R5-----------R6

 

All  routers have lo, for e.g R1 has 1.1.1./32, R2 2.2.2.2 so on

There are two tunnels terminating on 4.4.4.4 ( R4) as described below:

 

R1 is head end for tunnel 1.

interface tunnel 1

interface Tunnel1
 ip unnumbered Loopback0
 tunnel destination 4.4.4.4
 tunnel mode mpls traffic-eng
 tunnel mpls traffic-eng path-option 10 dynamic
 no routing dynamic

 

R1 tunnel 1 is along R1--R2-R3-R4

 

 

R5

nterface tunnel 1

interface Tunnel1
 ip unnumbered Loopback0
 tunnel destination 4.4.4.4
 tunnel mode mpls traffic-eng
 tunnel mpls traffic-eng path-option 10 dynamic
 no routing dynamic

 

R5 tunnel1 along R5-R2-R3-R4

 

++++++++++++++++++++++++++++++++++++

 

1)  Assume everything is configured properly, and both tunnels are up.

 

How does R2 ( which is mid point for both tunnels) distinguish between the two tunnels ?

 

For example:

 

R1 send path message with following info ( omitted for brevity)

Session :

destination address 4.4.44

tunnel id :1

Extended tunnel id: 1.1.1.1

 

Sender template:

lsp id :1

sender address 1.1.1.1

 

 

 

R5 path message:

 

Session :

destination address 4.4.44

tunnel id :1

Extended tunnel id: 5.5.5.5

 

Sender template:

lsp id :1

sender address 5.5.5.5

 

So if we look at both path message , R2 should be able to distinguish these are two different Path messages, How does R2 do that?  Will R2 consider session and sender template consider to determine that?

If yes, then we have an issue if we are providing link protection.

 

Assume R2 is PLR, R3 is MP, a back up tunnel is already established from PLR to MP so the link between R2--R3 is protected, PLR is configured to provide protection to tunnel 1 on R1 if the link R2-R3 fails.

 

Let say link R2-R3 fails, R2 is sending all the traffic from R1 traversing tunnel1, through back up tunnel.

 

According to my book, PLR ( R2) will also do the following:

 

Path message which usually R2 sends for tunnel 1 on R1 to R3,( to maintain reservation) will also be sent down back up tunnel but before R2 does that, it changes the sender address from 1.1.1. 1 to 2.2.2.2 in path message and then send it down the back up tunnel to MP ( R3)

 

 

The end result is R3 receives a path message ( for tunnel1 on R1) with sender address 2.2.2.2   So If R2 does indeed use  sender address  in sender template, to distinguish between the path messages from tunnel 1 on R5, then R2 should drop the reservation for tunnel 1 on R1 as sender address is 2.2.2.2 not 1.1.1.1

 

 

 

Sorry for this long winded post but i want to get my point across.

 

I appreciate your help.

 

 

Thanks

 

 

 

 

 

 

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

 All RSVP reservations are

 

All RSVP reservations are uniquely identified with a five-tuple of {Sender Address, LSP ID, Endpoint Address, Tunnel ID, Extended Tunnel ID}. The first two items in this five-tuple are found in the SENDER_TEMPLATE (and FILTER_SPEC) objects; the last three are found in the SESSION object. If two Path message are seen in which all five of these are the same, then only they are considered two representatives of the same reservation. So based on this, if we look at scenario you detailed each node would be able to differentiate between two different tunnel.

2 REPLIES
New Member

 All RSVP reservations are

 

All RSVP reservations are uniquely identified with a five-tuple of {Sender Address, LSP ID, Endpoint Address, Tunnel ID, Extended Tunnel ID}. The first two items in this five-tuple are found in the SENDER_TEMPLATE (and FILTER_SPEC) objects; the last three are found in the SESSION object. If two Path message are seen in which all five of these are the same, then only they are considered two representatives of the same reservation. So based on this, if we look at scenario you detailed each node would be able to differentiate between two different tunnel.

Bronze

 Thanks AqeelLets revisit my

 

Thanks Aqeel

Lets revisit my example.

R1---------R2----------R3----R4

                 |                |

                 |                |

                R5-----------R6

 

Lets assume no failure occurs, traffic from R1 is using tunnel1 to reach R4 ( R1-R2-R3-R4)

Let focus on R3

As long R3 is receiving path message from R2, R3 will continue to maintain reservation for the tunnel 1 on R1. As you mentioned R2 identifies path message belonging to a specific reservation  byusing 5 tuple ( session  object, sender object)

 

 

R2 is PLR , R3 is Mp,  let assume link bw R2--R3 goes down, R2 starts using back up tunnel to forward traffic from R1 primary's tunnel .

 

According to my book, R2 will also do the following:

 

 

R2 sends the path message it used to send to R3, down the back up tunnel  otherwise R3 will drop the reservation it is currently holding for R1's tunnel.

 

But before R2 does that, R2 modifies sender address in sender object ( that sender address was 1.1.1.1 in sender object)  and send the path message down the back up tunnel.

 

But R3 needs path message with same 5 tuple to continue to hold reservation for R1's tunnel, so when R3 receives the path message with different sender address in sender object i.e 2.2.2.2 instead of 1.1.1.1, should it not cause R3 to drop reservation for R1's tunnel1

 

I appreciate your help.

 

 

Thanks and have a great weekend.

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